Telephone-exchange system.



G. BABOOOK. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 7, 1905.

Patented Feb. 23, 1909.

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through the transmitter circuit.

UNITED STATES PATNT QFFTCE.

GARRISON BABGOCK, OF ROCHESTER, NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

To all whom it may concern:

Be it known that I, GARRrsoN BABCOCK, citizen of the United States,residing at Rochester, in the county of Monroe and State of New York,have invented a certain new and useful Improvement in Telephone-Exchange Systems, of which the following is a full, clear, concise, andexact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to telephone exchange systems and has for itsobject a more simplified and a more eflicient arrangement of theapparatus and circuits, particularly in central energy systems.

By means of my invention I am enabled to prevent the voice currentsissuing from the transmitter at one substation from being audible in,the receiver at that substation and only audible in the receiver at theother connected substation.

Another feature of my invention lies in the absence of all inductive ortransformer means at the substations and in the provision of commontransformation means at the central exchange. I also provide improvedindicating and supervisory signaling means, the indicating lamp or othersignal serving also as the supervisory signal.

In my system the direct current for supplying the transmitters at thesubstation-s passes parallelly over the line limbs while the telephonicvoice currents pass serially through the line limbs. The resistance tothe direct current is therefore practically reduced to one-fourth theresistance encountered in systems of the prior art with the same sizeconductors, or in other words, to produce as efficient results as inprior systems practically only one-fourth the cross section of conductorwould be necessary. At the substations the receiver coils are includedserially in the line limbs and from a point between the coils thetransmitter circuit leads to ground. Iormally the central battery isconnected between ground and through an indicating relay with both linelimbs, and upon closure of the transmitter circuit at the substationcurrent flows from the battery parallelly through the line limbs,differentially through the receiver coils and The cord circuit at thecentral exchange is divided into two inductively separated partsprovided with repeating coils which inductively Specification of LettersPatent.

Application filed July '7, 1905.

Patented Feb. 23, 1909.

Serial No. 268,756.

repeat the voice currents from one line to the other connected line, andthese repeating coils are so arranged that when conversation is going onbetween two substations, the voice currents from either substation willpass differentially and parallelly through the receiver coils throughthe corresponding repeating coils at the central exchange, where theyare rearranged to flow serially through the line limbs of the othersubstation and serially through the receiver coils thereat. Thus thereceiver at a substation is not responsive to the voice currents fromthat substation but is responsive only to the voice currents coming fromthe other substation.

My invention will be best understood by reference to the accompanyingdrawing which diagrammatically shows one form of system in which theseveral features of my invention may be utilized.

The line limbs ab lead from the jack springs 1 and 2 and at thesubstation include serially the coils 3 and 1 of the receiver 5. Thetransmitter circuit thus leads from a point 7 between the receiver coilsto the contact 8 of the switch hook 9 and includes the transmitter 10,the switch hook being connected with ground G. The alternate jacksprings 11 and 12 are normally in engagement with the main springs 1 and2 and both connect with the conductor 13 containing the winding 14 ofthe indicating relay 15 and connect with the positive side of the commonbattery B. A' lamp or other signal 16 is included in the conductor 17leading from the negative side of the battery B to the front contact 18of the indicating relay and to the jack thimble 19.

At the central exchange are cord circuits C each provided with the plugs20 and 21. Each plug is associated with two sets of repeating coils, oneset including the repeating coils 22 and 23 and the other set includingthe repeating coils 22 and 23. The sleeve and tip members of the plug 20are connected together through two parallel paths, one path includingthe primary windings 21 and 25 of the coils 22 and 23 respectively, andthe other path including the secondary windings 26 and 27 of the coils22 and 23. The sleeve and tip members of the plug 21 are also connectedtogether through parallel paths, one including the primary windings 2iand 25 of the coils 22 and 23 respectively, and the secondary windings26 and 27 of the coils 22 and 23. The conductor 28 1 leads from thepositive side of the battery to a point between the primary windings 22and 23 and includes the Winding of the supervisory relay 29. Theconductor 30 leads from the positive side of the battery and to a pointbetween the primary wind- I ings 22 and 23 and includes the winding ofthe supervisory relay 31. The armature 32 of the relay 29 is connectedwith the positive pole of the battery, and the normal contact33theret'or is connected with the sleeve member of the plug 20. Thearmature 34 of the relay 31 connects with the positive pole of thebattery, and the normal contact 35 therefor connects with the sleevemember of the plug 21.

The operation of a system of this kind is now apparent. Upon removal ofthe receiver from the hook the transmitter circuit at the substation isconnected with ground and current will flow as follows: from thepositive pole of the battery at the central exchange through the trunkconductor 36 to the conductor 13, through winding 14 of the indicatingrelay and to the normal spring contacts 11 and 12, the current thenpassing parallelly through the main jack springs 1 and 2 and through theline limbs 64 and b parallelly through the receiver coils 3 and a andthrough the transmitter circuit at the substation to ground, thenegative side of the central battery being also grounded. The indicatingrelay becomes energized to attract its armature 37 against its contact18 whereupon circuit will be closed through the lamp 16 from the batterythrough the conductor 1?, through contact 18 and attracted armature 37,the lamp 16 being illuminated to notify the operator who inserts theplug 20 into the corresponding springjack. Insertion of the plug,however, lir'ts the main springs 1 and 2 from the normal contact springs11 and 12 thus opening the circuit through the indicating relay and thecircuit controlled thereby through the lamp. The primary windings 24 and25 of the repeating coils 22 and 23, however, are connected parallellyin circuit and posiive battery is fed to the line and substation throughthe relay 29 and conductor 28. Consequent energization of the relay 29causes attraction of its armature 32 to prevent closure of a circuitthrough the lamp 16 upon insertion of a plug in the jack, which circuitthrough the lamp would otherwise be closed through the circuit includingthe conductor 17 the ack .thimble 19, the sleeve member of the plug 20,the contact 33 and the armature 32, the circuit controlling the relay 29being in turn controlled by the condition of the substation apparatus. Ihave not shown operators telephonic apparatus or ringing apparatus, asthe principles of my invention can be illustrated without such becomingilluminated.

connections. But supposing connection is desired with the substationshown at the right of the diagram. The operator inserts the plug 21 intothe corresponding springjack which then immediately closes a circuitthrough the lamp 16, through the armature 3%, contact 35, sleeve memberof the plug 21, jack thimble 19 and conductor 17 the lamp Upon removingthe receiver from the hook in response to a calling signal however,circuit will be closed through the supervisory relay 31 to open thecircuit through the lamp 16, the circuit through the relay being tracedas follows: from the positive pole of the battery through relay 31parallelly through the primary windings 24. and 25, parallelly throughthe plug members and jack springs 1 and 2 and through the line limbs aand b, parallelly through the coils 3 and L of the receiver at thecalled station, and through the transmitt r circuit to ground, and thetwo substations are now telephonically connected. The current forsupplying the transmitter thus passes parallelly through the line limbsand through the receiver coils, and these coils being differentiallywound, voice currents from the corresponding transmitter will not beaudible in the receiver. In other words, the user of the telephone cannot hear his own voice. lis voice currents pass to the central exchangeand through the corresponding primary and secondary coils of therepeating mechanism, being there redirected to flow serially into theconnected line and through the line limbs, and consequently to flowserially through the receiver connected therewith and to be audible tothe user of this receive-r, whose voice currents pass parallelly throughthe receiver coils and are inaudible to him. The secondary windings 26and 27, for instance, are so associated with the primary windings 24:and 25 that the parallel direction of the voice currents from thecorresponding substation through these primary coils will be given aserial direction through the secondary coils and consequently throughthe line limbs of the other line. In the same manner the secondarywindings 26 and 27 of the relays 22 and 23 are arranged to cause serialcurrent flow in the other line of the induced voice currents flowingparallelly through the primary windings 24 and 25. This parallelarrangement, as is evident, greatly reduces the required cross sectionof conductor. The annoyance due to extraneous noises. in the transmitteris also entirely obviated. The primary windings of the repeating coilsare preferably of suflicient impedance to prevent leakage of voicecurrents, cross-talk and so on, while the corresponding primary andsecondary windings are preferably in opposition to render the repeatingcoil noninductive to allow free passage of telephonic ourrents betweenthe connected substations. After the subscribers have finishedconversation, the receivers are replaced on the hooks, thus breaking thecircuit through the respective supervisory relays, and the armatures ofthese relays falling back to their normal contacts close circuit throughthe respective signal lamps to notify the operator that conversation isended. The same lamp or other signal, therefore, serves both as anindicating signal and as a supervisory signal.

In a system of this kind there will be considerably less trouble, bothline limbs being at the same potential and in parallel, and should oneline limb become broken, for instance, or in any other way defective,the subscriber can still call the central exchange over the otherconductor, and, although it may be difficult to converse, sutlicientsignals can be given .to notify the central exchange that the line isout of order. To further balance the line, adjustable resistances 38 and39 may be included in the line limbs, and this resistance is preferablyin the form of heat coils which then serve the combined purposes ofprotecting the line against overflow of current and also to balance theline limbs.

The calling circuit at the substations may be connected with the linelimbs in various ways, being here shown in bridge across the limbs andincluding the signal bell 40 and the condenser 41. The ringingarrangement at the central exchange will then be connected with the cordcircuit to properly send signaling current for the substation signalcircuit.

I thus provide a very simple, economical and eflicient telephone system,but do not wish to be limited to this particular adaptation thereofshown, as the features thereof may be utilized with equal efliciency inlocal battery and other system arrangements.

Having described the principle of my invention, however, I claim as newand desire to secure by Letters Patent:

1. In a telephone system, the combination with a substation, of linelimbs leading therefrom, means at the substation for transmittingtelephonic currents, means at the substation for receiving telephoniccurrents, means for causing the transmitted currents to pass parallellyover the line limbs, and means for causing the received telephonecurrents to pass serially through the line limbs.

2. In a telephone system, the combination with a telephone line, ofsubstations connected therewith, transmitting and receiving apparatus ateach substation associated with the line, a common source of current forsupplying the line and apparatus, means for causing telephonic currentsfrom the transmitting apparatus at one substation to flow in such amanner through the receiving apparatus at said substation as to rendersaid receiving apparatus irresponsive to such current flow, and meansfor causing said current flow to pass in such manner through thereceiving apparatus at a connected substation as to cause said otherreceiving apparatus to be responsive.

In a telephone system, the combination with substations, of a lineconnecting said substations, a source of current for supplying the lineand substations, a transmitter and a receiver at each substationassociated with the line limbs thercat, and means associated with theline for causing telephonic currents transmitted from one substation tolow parallelly through the receiver thereat and through the line limbsof said substation and to flow serially through the line limbs andthrough the receiver of a connected substation, whereby the receiver atthe connected substation only is responsive to said currents.

at. In a telephone system, the combination with substations connected bya telephone line, of a source of current for supplying said line andsubstations, a transmitter and a receiver at each substation associatedwith the line limbs thereat, and means associated with the line forcausing telephonic currents transmitted from a substation to flowparallelly through the receiver coils and the line limbs and for causingtelephonic currents received at the substation to pass serially throughthe receiver coils.

In a telephone system, the combination with substations connected by atelephone line, of a source of current for supplying the line atsubstations, a receiver and a transmitter at each substation connectedwith the line therea't, and means for causing telephonic currentstransmitted from a substation to pass dilferentially through the coilsof the receiver at said substation and parallelly through the line limbsleading therefrom and for causing telephonic currents received at thesubstation to How serially through the line limbs and receiver coils,whereby said receiver is irresponsive to transmitted currents andresponsive only to received currents.

6. In a telephone system, the combination with two substations, of linelimbs leading therefrom, a source of current for supplying said linelimbs and substations, a transmitter and a receiver at each substation,means adapted upon actuation of the transmitter at one substation forcausing the generated telephonic currents to flowfrom the substationparallelly through the line limbs and through the receiver coils,whereby the receiver is irresponsive, means associated with the linelimbs leading from each substation for rearranging the parallel currentsfrom a substation to cause them to flow serially through the line limbsof the other substation and the receiver coils thereat, whereby thereceiver at the other substation is responsive to the currentstransmitted from the first substation.

T. In a telephone system, the combination with two substations, of linelimbs leading from each substation, receiving and transmitting apparatusat each substation, means adapted upon actuation of the transmittingapparatus at a substation for causing the generated telephonic currentsto flow parallelly through the line limbs, means for causing thereceiving apparatus to be irre sponsive upon such parallel current flow,i11- ductive means associated with the line limbs from each substationfor rearranging the parallel current flow received thereby and causingthe on rent to flow serially through the line limbs of the othersubstation and the receiving apparatus thereat, and means for causingthe receiving apparatus to be responsive to such serial current flow.

8. In a telephone system, the combination with two substations, of linelimbs leading from each substation, transmitting and receiving apparatusat each substation, a source of current for supplying the line limbs andsubstation apparatus, means operable upon actuation of the transmittingapparatus at one of the substations for causing telephonic currents toflow parallelly over the line limbs from the substation, means forcausing the transmitting apparatus at the substation to be irresponsiveto such parallel current flow, inductive means connected with the linelimbs for receiving the telephonic currents from the line limbs of thefirst substation and inducing these currents to the line limbs of theother substation, said inducing means being arranged to cause theinduced currents to flow serially through the line limbs of the othersubstations and the receiving apparatus thereat, and means for causingthe receiving apparatus to be responsive to such serial current flow.

9. In a telephone system, the combination with two substations, of linelimbs leading from each substation, a transmitter and a receiver at eachsubstation, a common source of current for supplying the line limbs andtelephonic apparatus at the substations, means operable upon actuationof the transmitter at either of the substations for causing thegenerated telephonic currents to flow parallelly through the receivercoils and through the line limbs whereby the receiver is renderedirresponsive to the transmitted telephonic currents, inductive mechanismassociated with the line limbs from each substation for receiving thetelephonic currents transmitted from one substation and for in ducingsaid currents to the line limbs of the other substation, said lnductivemeans being arranged to cause the induced currents to tlow seriallythrough the line limbs of the other substation whereby the receivercoils at the other substation are included serially in circuit and thereceiver rendered respon sive to received currents.

10. In a telephone system, the combination with a central exchange, oftelephone lines leading therefrom and terminating in substations, asource of current at the exchange for supplying the lines, transmittingand receiving apparatus at each substation, and means for causingtelephonic currents transmitted from one substation to flow parallellythrough the line limbs to the central exchange and serially through theline limbs of a connected substation from the central exchange, thereceiving apparatus being irresponsive to telephonic currentstransmitted from the substation but responsive to currents received atthe substation.

11. In a telephone system, the combination with a central exchange, oftelephone lines leading therefrom and terminating in a substation, acord circuit at the exchange for connecting said lines together,repeating coils connected with the cord circuit, a transmitter and areceiver at each substation, and means adapted upon actuation of thetransmitter at either substation for causing the generated telephoniccurrents to flow parallelly and differentially through the receivercoils and through the line limbs to the repeating coils, said repeatingcoils causing the transmitted current to be induced to the line limbs ofthe other substation and to flow serially through said line limbs andthrough the coils of the receiver thereat, each receiver beingresponsive to currents flowing serially through the line limbs butirresponsive to currents flowing parallelly through the line limbs.

12. In a telephone system, the combination with a central exchange, oftelephone lines leading therefrom and terminating in a substation, acord circuit at the central exchange, inductive repeating mechanismconnected with the cord circuit, transmitting and receiving apparatus ateach substation, a source of current at the central exchange, means forcausing direct currents from said source to flow parallelly through therepeating apparatus and the line limbs, and means for causing telephoniccurrents to tic parallelly over the line limbs from a substation to therepeating apparatus and serially over the line limbs from the repeatingapparatus to the substation.

13. In a telephone system, the combination with a central exchange, oftelephone lines leading therefrom to substations, transmitting andreceiving apparatus at each substation connected with the line limbsthereat, a source of current at the central exchange, means for causingdirect currents to flow parallelly through the line limbs, and means forcausing telephonic currents to fiow parallelly over the line limbstoward the central exchange and serially over the line limbs from thecentral exchange.

14. In a telephone system, the combination with a central exchange, oftelephone lines leading therefrom to substations, transmitting andreceiving apparatus at each sub station connected with the line limbsthereat, a source of current at the central exchange, means for causingdirect currents to flow parallelly through the line limbs, means forcausing telephonic currents to flow parallelly over the line limbstoward the central exchange and serially over the line limbs from thecentral exchange, means for causing the receiving apparatus to beirresponsive to telephonic currents flowing from the correspondingsubstation, and means for causing the receiving apparatus to beresponsive to telephonic currents received at the correspondingsubstation. Q

15. In a telephone exchange system, the combination with a centralexchange, of telephone lines leading therefrom to sub stations,transmitting and receiving apparatus at each substation, means forcausing transmitter currents to flow in parallel over the line limbs tothe central exchange, a cord circuit in the central exchange for connecting telephone lines together, an induction coil serving to convertthe transmitter currents received thereby into currents for actuatingthe receiving apparatus at the connected substation, said induction coilserving also to rearrange the current flow to cause the current to flowserially through the line limbs and through the receiving apparatus atthe connected substation.

16. In a telephone exchange system, the combination with a centralexchange, of substations connected therewith to telephone lines, areceiver and a transmitter at each substation, a source of current forsupplying the line and apparatus at the substations, means for causingthe transmitter currents to flow from a substation parallelly throughthe receiver coils and through the line limbs in the central exchange,and adjustable means included in the line limbs for adjusting thecurrent flow therethrough.

17 In a telephone exchange system, the combination with a centralexchange, of substations connected therewith to telephone lines, areceiver and a transmitter at each substation, a source of currentforsupplyiug the line and apparatus at the substations, means for causingthe transmitter currents to flow from a substation parallelly throughthe receiver coils and through the line limbs to the central exchange,and heat coils included in the line limbs for protecting againstexcessive current flow and for balancing the current flow through theline limbs.

In a telephone exchange system, the combinatioi'i with a centralexchange, of substations connected therewith to telephone lines, areceiver and a transmitter at each substation, a source of current forsupplying the line and apparatus at the substations, means for causingthe transmitter currents to flow from a substation parallelly throughthe receiver coils and through the line limbs to the central exchange,and adjustable resistances in the form of heat coils included in theline limbs for balancing the current flow tl'ierethrough and forprotecting against excessive current flow.

In witness whereof, I hereunto subscribe my name this first day of JulyA. D., 1905.

GARRISON BABCOGK.

Witnesses CHARLES J. SCHMIDT, Lnoxnnn W. NOVANDER.

